#main{
    width: 408px;
    height: 408px;
    background: white;
    border: 2px solid gray;
    margin: 0 auto;
    overflow: hidden;
}
h2{
    text-align: center;
}
#con{
    width: 100%;
    height: 400px;
    position: relative;
    top: -408px;/*隐藏所有格子*/
    border-collapse: collapse;
}

/*行*/
.row{
    height: 100px;
    width: 100%;
}
/*一个块*/
.cell{
    height: 100px;
    width: 100px;
    float: left;
    border: rgb(54, 74, 129) 1px solid;
}
.black{
    background: black;
}
.btn{
    width: 100%;
    text-align: center;
}
.start{
    margin: 20px auto;
    width: 150px;
    height: 50px;
    border-radius: 10px;
    background: yellowgreen;
    line-height: 50px;
    color: #fff;
}
